Parts help for my 1970

[Mark Trent]

I need some clarification on a few parts.

First the gas tank for a 1970 350 L46. The owner's manual says 20gal. tank. Is part #3967746 the correct tank for me? It is a non-eec car built in Feb.

Next, the thermostat. NCRS ops manual & test guide on pg.38, says "All vehicles came equipped with a 195 F thermostat, except LT1's and LS6's which had a 180-degree F unit." However, my owner's manual says 180F. Who is correct?

Finally, the master cylinder: is there a way to tell if it is original. If not, what should an authentic replacement look like or have on it? I have manual brakes.

Thank you - Mark

[Jim T.]

Re: Parts help for my 1970

20 gallon gas tank came on my 70 and the owners manual is correct as to the 180F thermostat that came in my car. My original did fail driving on an interstate one hot August day. Have power brakes not manual.

[Joe L.]

Re: Parts help for my 1970

Mark-----

The fuel tank for your 1970 L-46 application is a 20 gallon capacity tank. The GM #3967746 tank is not the correct tank for your application, though. The 3967746 has no provisions for a fuel return on the PASSENGER side and is designed for use with applications using a Holley carb. For Holley carb applications, there is no PASSENGER SIDE fuel return line. For 1970 the 3967746 fuel tank was used only for LT-1 applications without EEC (it would also have been used for LS-7 if any had been built). Your L-46 application requires a GM #3967741 fuel tank. This tank has a PASSENGER side fitting for the fuel return line from your AC type 40769 fuel pump.

EEC applications have a DRIVER side fuel return fitting + PASSENGER side fitting (for Q-Jet applications) and a DRIVER side ONLY fitting (for Holley applications). The "with EEC" fuel tanks are GM #3967749 for Q-Jet applications and GM #3967755 for Holley applications. The GM #3967755 tank was discontinued by GM in October, 1982 but is available from Quanta in reproduction for those folks with 1970 California-delivered LT-1s and all 1971-72 LT-1 and LS-6.

If the ops and tech manual says that all cars were supplied with 195 degree thermostats except LT-1 and LS-6 with 180 degree, then the manual has it backwards. The LT-1 and LS-6 engine applications use the 195 degree thermostat (since they are also equipped with AIR). All other applications use the 180 degree thermostat.

Your master cylinder, if original or a correctly configured replacement, should be a GM #5455509 casting, have a "DC" stamped on the front "half-moon" shaped machined surface, and have bleeder valves. It may or may not have a date stamped on the front brake line machined surface. If original, this date should be consistent with the build date of the car.

[Mark Trent]

Re: Parts help for my 1970

Joe - thank you very much for the information. I would have bought the wrong tank, for sure! Mark

[Joe L.]

Minor Correction

It occurs to me that I mis-spoke regarding one thing in my original post. I mentioned that for Holley applications there is no passenger side fuel return line and that the GM #3967755 fuel tank was used for LS-6 applications with EEC. Neither one of those statements are correct. There is ONE Holley application that DOES use a passenger side fuel return line. That application is 1971 with LS-6. Since ALL 1971 applications, including LS-6, had EEC, the fuel tank used for the LS-6 application was the same as that used for all non-LT-1 applications----GM #3967749. This tank has the fuel return fittings on BOTH the passenger side (for fuel pump originating return) and the driver side (for EEC system return).

This also brings up a point of Corvette trivia, that being that the 1971 Corvette LS-6 was the ONLY Corvette ever built which used a Holley carburetor AND also used a passenger side fuel return line. Now, how many of you were aware of that fact?